JP2007014148A - Power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate imbalance of batteries, without wasting the power charged in the batteries. <P>SOLUTION: A power supply is provided with a plurality of batteries 1 connected in series; an equalization circuit 2 for detecting residual capacities of the batteries 1 that detects the battery, having the excessive residual capacity larger than a setting value, connecting the battery 1 having the excessive residual capacity to a capacitor 3 or a backup battery 4, reducing the excessive residual capacity and balancing the residual capacities of the batteries 1; and a power supplying circuit 5 for supplying a load with power charged in the capacitor 3 or the backup battery 4. The power supply charges the capacitor 3 or the backup battery 4, by using the battery having excessive residual capacity, supplies the load with power from the capacitor 3 or the backup battery 4, and equalizes the residual capacities of the batteries 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is a power supply device in which a plurality of batteries are connected in series, and a power supply that charges and discharges a battery while maintaining the remaining capacity of each battery uniformly and preventing overcharge and overdischarge of a specific battery. Relates to the device. In particular, the present invention relates to a power supply apparatus that is optimal as a power supply that supplies power to a motor that drives a vehicle.

  A power supply device in which a plurality of batteries are connected in series is used for various applications. In particular, since this type of power supply device can increase the output voltage by increasing the number of batteries connected in series, it is used for applications that require high output, such as a power supply for a motor that drives a vehicle. When a large number of batteries are connected in series and charged, the same current flows through all the batteries, but each battery gradually becomes unbalanced. This is because the electrical characteristics of all the batteries or the environment (for example, temperature variation) during charging / discharging cannot be made uniform. A battery having a reduced capacity due to deterioration is more likely to be overcharged or overdischarged compared to other batteries. Battery overcharging and overdischarging cause battery performance to deteriorate. In particular, in a power supply device in which a large number of batteries are connected in series, the performance degradation of a specific battery affects the whole. This is because charging / discharging is controlled while protecting the deteriorated battery.

In order to eliminate this drawback, a method has been developed in which a discharge circuit is connected to batteries connected in series and the voltage balance of the batteries is made uniform by the discharge circuit. (See Patent Document 1)
Japanese Patent Laid-Open No. 5-49181

  The apparatus described in the above publication has a discharge circuit 22 connected in parallel with a battery 21 as shown in FIG. The discharge circuit 22 has a discharge resistor 27 and a switching element 28 connected in series. The discharge circuit 22 switches on the switching element 28 and discharges the connected battery 21 with the discharge resistor 27. The switching element 28 is controlled to be turned on / off by the output of the comparator 23 that compares the battery voltage with the set voltage.

  In the power supply device including the voltage balance circuit, when the voltage of any battery 21 becomes higher than the set voltage, the comparator 23 connected to the battery 21 turns on the switching element 28. The comparator 23 connected to the battery 21 whose voltage does not become higher than the set voltage is turned off without switching the switching element 28 on. In this state, the switching element 28 switched on discharges the battery 21 through the discharge resistor 27. The discharge circuit 22 in which the switching element 28 cannot be switched on does not discharge the battery 21 connected thereto. When the voltage of the battery 21 discharged by the switching element 28 and the discharge resistor 27 gradually decreases and becomes lower than the voltage at which the discharge is stopped, the switching element 28 is switched from on to off and the discharge is stopped.

  This power supply device discharges a battery having a high voltage, that is, a battery having a large remaining capacity with a resistor. For this reason, in order to eliminate battery imbalance, the resistor wastes power. Since the electric power consumed by the resistor is supplied to the battery by a charger (not shown), this device has a disadvantage of wasting electric power in order to eliminate battery imbalance.

  The present invention has been developed for the purpose of solving this drawback. An important object of the present invention is to provide a power supply device that can eliminate battery imbalance without wasting power consumed by the battery.

  The power supply device of the present invention detects a plurality of batteries 1 that are directly connected to each other, and detects an excessive capacity battery that has a remaining capacity larger than a set value by detecting the remaining capacity of each battery 1. The determined battery 1 is connected to the capacitor 3 or the spare battery 4, and the capacitor 3 or the spare battery 4 is charged with the equalizing circuit 2 that balances the remaining capacity of the battery 1 by reducing the remaining capacity of the excessive capacity battery. And a power supply circuit 5 for supplying the power to the load. The power supply device charges the capacitor 3 or the spare battery 4 with an excessive capacity battery, supplies power from the capacitor 3 or the spare battery 4 to the load, and equalizes the remaining capacity of each battery 1.

  In the power supply device of the present invention, the capacitor 3 or the spare battery 4 can supply power to the temperature control device 8 that controls the temperature of the battery 1. In the power supply device of the present invention, the condenser 3 or the spare battery 4 supplies power to the motor of a fan that forcibly blows air to the battery 1 or supplies the cooling medium to the battery 1 to set the battery temperature to the set temperature. It is possible to supply electric power to the motors of the Peltier element or to supply power to a Peltier element that keeps the battery temperature at a set temperature.

  The power supply device of the present invention realizes a feature that can eliminate battery unbalance without wasting power consumed by the battery. The power supply device of the present invention detects the remaining capacity of the battery and connects the battery determined to be an excessive capacity battery to a capacitor or a reserve battery, and discharges the excess capacity battery to the capacitor or the reserve battery to reduce the remaining capacity. This is because the power of the capacitor or the spare battery charged with an overcapacity battery is reduced and supplied to the load for effective use.

  Embodiments of the present invention will be described below with reference to the drawings. However, the embodiments described below exemplify a power supply device for embodying the technical idea of the present invention, and the present invention does not specify the power supply device as follows.

  Further, in this specification, in order to facilitate understanding of the scope of claims, numbers corresponding to the members shown in the examples are indicated in the “claims” and “means for solving problems” sections. It is added to the members. However, the members shown in the claims are not limited to the members in the embodiments.

  The power supply device shown in FIGS. 2 and 3 has a plurality of directly connected batteries 1, an equalization circuit 2 that eliminates and balances the unbalance of the remaining capacity of each battery 1, and a large remaining capacity. And a power supply circuit 5 for discharging the capacitor 3 and the spare battery 4 charged by the battery 1.

  The battery 1 is a lithium ion battery 1. However, the battery can be any battery that can be charged, such as a nickel metal hydride battery or a nickel cadmium battery, instead of the lithium ion battery. The battery 1 is connected in series, or a plurality of batteries are connected in series to form a battery module, and a plurality of battery modules are further connected in series.

  The equalization circuit 2 includes a detection unit 6 that detects the remaining capacity of each battery 1 and detects an excessive capacity battery whose remaining capacity is larger than a set value, and a switch 7 that is switched by the detection unit 6. The detection unit 6 in the figure detects the remaining capacity from the voltage of the battery 1, and determines that the battery 1 having a battery voltage larger than the set voltage is an over-capacity battery. However, the equalization circuit can detect a remaining capacity not only from the battery voltage but also from the charge / discharge current and temperature, and determine a battery having a larger remaining capacity than the set capacity as an overcapacity battery. The equalization circuit 2 ideally detects the excessive capacity battery by separately detecting the remaining capacity of all the batteries 1. However, the equalization circuit does not necessarily detect the remaining capacity of all the batteries, but detects the remaining capacity of the battery module in which a plurality of batteries are set in series. It can also be detected.

  The equalization circuit 2 controls the switch 7 by the detection unit 6 to connect the battery 1 determined to be an excessive capacity battery to the capacitor 3 or the spare battery 4 and discharge the excessive capacity battery to the capacitor 3 or the reserve battery 4. . In other words, the capacitor 3 and the spare battery 4 are charged with an excessive capacity battery. The switch 7 of the equalization circuit 2 can control the average current with which the overcapacity battery charges the capacitor 3 and the spare battery 4 with a duty for switching on and off. In particular, when an overcapacity battery is connected to the fully discharged capacitor 3, a large discharge current flows at the moment of connection. In order to limit the discharge current, the average current can be reduced by switching the switch 7 on and off at a predetermined cycle. The average current can be reduced by reducing the duty for switching the switch 7 on and off, that is, shortening the on-time with respect to the off-time. Thus, the equalization circuit 2 that limits the average current with the duty of switching the switch 7 on and off can limit the discharge current of the overcapacity battery without connecting a current limiting resistor in series with the switch 7. This circuit can efficiently charge the capacitor 3 and the spare battery 4 with an over-capacity battery without any power consumption of the current limiting resistor.

  An over-capacity battery that charges the capacitor 3 or the spare battery 4 has a smaller remaining capacity as it is charged. When the capacitor 3 and the spare battery 4 are charged and the remaining capacity becomes small, the detection unit 6 of the equalization circuit 2 switches the switch 7 from on to off to stop the discharge.

  The remaining capacity of the battery 1 increases when charged, and decreases when discharged. Therefore, the remaining capacity of the battery 1 exceeds the set value when the remaining capacity gradually increases after being charged. The excessive capacity battery that has been charged and whose remaining capacity exceeds the set value is discharged to the capacitor 3 and the spare battery 4 by the equalization circuit 2. The equalization circuit 2 discharges the overcapacity battery while charging the battery 1, or discharges the overcapacity battery after the charging is completed, or both when charging and when the charging is completed. The overcapacity battery is discharged at the timing. Therefore, the present invention does not specify the timing for discharging the overcapacity battery to the capacitor 3 or the spare battery 4 when the battery 1 is being charged. When the battery 1 is being charged, only the overcapacity battery is discharged, and the increase in the remaining capacity of the overcapacity battery can be reduced or reduced to equalize the remaining capacity, and the charging is stopped or terminated. This is because the remaining capacity can be reduced by discharging the excessive capacity battery at the timing.

  2 and 3 are mounted on a vehicle, and are connected to a generator 10 including an inverter 11 and a motor generator 12. The inverter 11 converts the direct current of the power supply device into alternating current, boosts a predetermined voltage, and supplies it to the motor generator 12. Moreover, the inverter 11 converts the alternating current generated by the motor generator 12 into a direct current and also converts it into a voltage for charging the battery 1 of the power supply device. The inverter 11 is controlled by a vehicle ECU (not shown) mounted on the vehicle, supplies electric power from the battery 1 to the motor generator 12, and drives the vehicle with the motor. Further, when the motor generator 12 is rotated by regenerative braking for braking the vehicle or by the engine of the vehicle, the motor generator 12 generates electricity. The electric power generated by the motor generator 12 is supplied to the power supply device via the inverter 11 to charge the battery 1. The generator 10 mounted on the vehicle shown in the figure charges the battery 1 of the power supply device with a motor generator 12 used in combination with the motor and the generator. However, the generator of the vehicle can be provided with a generator separately from the motor, and the output of this generator can be supplied to the power supply device by an inverter to charge the battery.

  The battery 1 charged by the motor generator 12 or the generator is connected in series and charged with the same current, but the remaining capacities of all the batteries 1 are not equal. For this reason, the equalization circuit 2 detects the remaining capacity of each battery 1, and when the remaining capacity of the battery 1 becomes larger than a set value, it determines with an overcapacity battery and discharges it forcibly. The excessive capacity battery is discharged by charging the capacitor 3 or the spare battery 4. Therefore, the capacitor 3 and the spare battery 4 are charged while the overcapacity battery is discharged.

  The power supply circuit 5 discharges the charged capacitor 3 and spare battery 4 by connecting them to a load. The power supply circuit 5 shown in the figure connects the capacitor 3 or the spare battery 4 to a temperature control device 8 that controls the temperature of the battery 1 and supplies power to the temperature control device 8. Since the power supply device for vehicles charges and discharges the battery 1 with a large current, the temperature of the battery 1 may increase. In particular, when charging / discharging with a large current when the outside air temperature is high, the battery temperature increases. When the battery 1 is charged and discharged in a state where the temperature is high, the battery 1 is deteriorated and its life is shortened. In addition, since charging efficiency and discharging efficiency vary depending on temperature, there are problems such as a difference in remaining capacity if there is a temperature difference in the battery 1. In order to prevent this adverse effect, the vehicle power supply device includes a temperature control device 8 that cools the battery 1 whose temperature has increased.

  The temperature control device 8 that cools the battery 1 includes a fan that forcibly blows and cools the battery, a circulation pump that supplies a cooling medium to the battery and sets the battery temperature to a set temperature, a Peltier element that holds the battery temperature at the set temperature, and the like It is. A fan that forcibly blows air to the battery is driven by a motor. The power supply circuit 5 can rotate the fan by connecting the capacitor 3 or the spare battery 4 charged with an excessive capacity battery to a fan motor that forcibly blows air. In addition, the power supply circuit 5 may operate the circulation pump by connecting the condenser 3 and the spare battery 4 to the motor of the circulation pump that circulates the cooling medium to the heat exchange effector that is thermally coupled to the battery 1. it can. Further, the power supply circuit 5 can cool the battery 1 by connecting the capacitor 3 and the spare battery 4 to the Peltier element thermally coupled to the battery 1 and energizing the Peltier element. The Peltier element can switch between heat generation and heat absorption in the direction of current. Therefore, the Peltier device thermally coupled to the battery 1 can also heat the supercooled battery 1 by controlling the direction of current.

  An apparatus in which the capacitor 3 or the spare battery 4 supplies power to the temperature control device 8 of the battery 1 can use the surplus power of the excessive capacity battery extremely efficiently. This is because the battery temperature increases when the specific battery 1 becomes an excessive capacity battery. The battery 1 has a property that the temperature increases when fully charged. Therefore, when any one of the batteries 1 becomes an excessive capacity battery, the temperature of the battery 1 is almost always high. Therefore, when the capacitor 3 or the spare battery 4 is charged with an excessive capacity battery, the temperature of the battery 1 is high. The capacity of the capacitor 3 and the spare battery 4 which are charged by self-discharge gradually decreases. In particular, the charged capacity of the capacitor 3 decreases with time as compared with the spare battery 4. For this reason, the charging power of the capacitor 3 and the spare battery 4 can be used more effectively as the time from the charging with the excessive capacity battery to the discharging is shorter. When the capacitor 3 or the spare battery 4 is charged, the battery temperature rises. Therefore, the fan motor or the circulation pump that cools the battery 1 is operated by the capacitor 3 or the spare battery 4 or the Peltier element is energized to operate the battery The device for cooling 1 can reduce the self-discharge of the capacitor 3 and can effectively supply the charged power to the temperature control device 8 without waste.

  The voltage of the capacitor 3 decreases as it is discharged. Therefore, the power supply circuit 5 that connects the capacitor 3 to the temperature control device 8 and rotates the motor or energizes the Peltier element incorporates an inverter that stabilizes the voltage of the capacitor 3. The inverter boosts the output voltage and stabilizes the output voltage as the voltage of the capacitor 3 decreases. The power supply circuit 5 can efficiently discharge the electric power stored in the capacitor 3 by supplying it efficiently to a load such as the temperature control device 8. The reserve battery 4 has a smaller decrease in output voltage relative to the remaining capacity than the capacitor 3. For this reason, it can discharge by supplying electric power to loads, such as the temperature control apparatus 8, without passing through an inverter. However, since the output voltage of the standby battery 4 also decreases as the remaining capacity decreases, power can be supplied to the load such as the temperature control device 8 via the inverter and discharged efficiently.

  The capacitor 3 and the spare battery 4 are charged with power discharged from the excessive capacity battery. For this reason, the electric power charged by the capacitor 3 and the spare battery 4 is limited. Accordingly, it is necessary to supply power to the load such as the temperature control device 8 from the capacitor 3 or the spare battery 4 and further supply power to the load such as the temperature control device 8 after the capacitor 3 or the spare battery 4 is completely discharged. If there is, electric power is supplied from an electrical equipment battery (not shown) mounted on the vehicle.

  The power supply apparatus described above uses the temperature control device 8 as a load for the capacitor 3 and the spare battery 4 charged with an excessive capacity battery. However, the power supply device mounted on the vehicle can supply power not only to the temperature control device 8 that controls the temperature of the battery 1 but also to a fan or an audio device used for air conditioning of the vehicle.

  The step in which the above power supply device equalizes the remaining capacity of each battery 1 will be described in detail with reference to the timing chart of FIG. In the following description, the process of equalizing the remaining capacity of each battery 1 using the power supply device shown in FIG. 2 is shown.

[Step 1]
In this step, the capacitor 3 is charged by discharging the excessive capacity battery.
(1) When the capacity C1 of the battery B1 is larger than the capacity C2 of the battery B2, the battery B1 is discharged using the battery B1 as an excessive capacity battery.
(2) At time t1, SW1 and SW3 are turned on. In this state, the battery B1 is connected to the capacitor 3, and the capacitor 3 is charged with the current discharged from the battery B1.
(3) The battery B1 is discharged until time t2, and the capacity of the battery B1 is reduced to C3. At time t2, SW1 and SW3 are switched off.
In this step, the battery B1 is discharged with a capacity C1-C3, and the capacitor 3 is charged with a capacity C4 (C4 = C1-C3).

[Step 2]
In this step, the charged capacitor 3 is discharged to charge the battery B2 having a small capacity.
(1) When the capacity C2 of the battery B2 is smaller than the capacity C3 of the discharged battery B1, the capacitor 3 is discharged to charge the battery B2.
(2) At time t3, SW2 and SW4 are switched on. In this state, the capacitor 3 is connected to the battery B2, and the battery B2 is charged by the current discharged from the capacitor 3.
(3) The capacitor 3 is discharged until time t4, and the capacity of the battery B2 is increased to C3. At time t4, SW2 and SW4 are switched off.
In this step, the capacitor 3 discharges the capacity C4-C5, and the battery B2 is charged with the capacity C3-C2 (C3-C2 = C4-C5) by this discharge. In this state, the capacity of each battery is equalized to C3.

  In this step, since the battery B2 having a small capacity is charged by the charged capacitor 3, the remaining capacity of each battery 1 can be made uniform by both discharging and charging. However, the charged capacitor can be discharged only to the temperature control device 8 without necessarily charging a battery having a small capacity. At this time, the discharge amount of the overcapacity battery in step 1 is adjusted to equalize the capacity of each battery.

[Step 3]
In this step, the electric power remaining in the charged capacitor 3 is discharged.
(1) At time t5, switch SW5 is turned on. In this state, the capacitor 3 is connected to the temperature control device 8 and discharged.
(3) The capacitor 3 is discharged until time t6, and the capacitance of the capacitor 3 is reduced to zero. At time t6, SW5 is switched off.
In this step, the capacitor 3 discharges the capacitance C5.

It is a circuit diagram of the conventional power supply device. It is a block diagram of the power supply device concerning one Example of this invention. It is a block diagram of the power supply device concerning the other Example of this invention. It is a timing chart which shows the process in which the power supply device shown in FIG. 2 equalizes the remaining capacity of each battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Battery 2 ... Equalization circuit 3 ... Capacitor 4 ... Spare battery 5 ... Power supply circuit 6 ... Detection part 7 ... Switch 8 ... Temperature control apparatus 10 ... Generator 11 ... Inverter 12 ... Motor generator 21 ... Battery 22 ... Discharge circuit 23 ... Comparator 27 ... Discharge resistor 28 ... Switching element

Claims (5)

A plurality of batteries (1) connected in series and the remaining capacity of each battery (1) were detected, and an overcapacity battery with a remaining capacity larger than the set value was detected, and determined as an overcapacity battery. An equalization circuit (2) for connecting the battery (1) to the capacitor (3) or the spare battery (4), reducing the remaining capacity of the overcapacity battery and balancing the remaining capacity of the battery (1), and the capacitor ( 3) or a power supply circuit (5) for supplying power charged in the reserve battery (4) to the load,
Charge the capacitor (3) or spare battery (4) with an over-capacity battery, and supply power to the load from the capacitor (3) or spare battery (4) to equalize the remaining capacity of each battery (1) A power supply unit configured as described above.   The power supply device according to claim 1, wherein the capacitor (3) or the reserve battery (4) supplies power to a temperature control device (8) for controlling the temperature of the battery (1).   The power supply device according to claim 1, wherein the capacitor (3) or the reserve battery (4) supplies electric power to a motor of a fan that forcibly blows air to the battery (1).   The power supply device according to claim 1, wherein the capacitor (3) or the spare battery (4) supplies electric power to a motor of a circulation pump that supplies a cooling medium to the battery (1) and sets the battery temperature to a set temperature. The power supply device according to claim 1, wherein the capacitor (3) or the spare battery (4) supplies electric power to a Peltier element that maintains the battery temperature at a set temperature.

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